Objective To purify marmoset serum IgG, prepare and identify the antiserum and the rabbit anti?marmoset antibody IgG?HRP (horseradish peroxidase). Methods Using SDS?PAGE analysis to identify the serum IgG from HiTrap ^TM Protein G. The antiserum titer was determined by double immunodiffusion assay. The rabbit anti?marmoset IgG was labeled with HRP by improved sodium periodate method. ELISA and western blotting were used to evaluate the concentration and specificity of rabbit anti?marmoset IgG?HRP. Results The purity of purified marmoset serum IgG determined by SDS?PAGE was higher than 95%, and the anti?serum titer of the anti?marmoset IgG polyclonal antibody was 1∶ 64. The concentration of rabbit anti?marmoset IgG?HRP identified by direct ELISA was 1∶ 256 000, and that by western?blotting was 1∶ 15 000, with a strong specificity. ConclusionsThe IgG?HRP marker antibody is prepared and the specificity and concentration are identified by ELISA and western blotting. It reserves the resources for the detection system of marmoset pathogens and the molecular immunological testing system.